1. Field of the Invention
The present invention relates to an image reader and particularly to a mechanism for retaining a platen glass mounted on a stationary or moving original type image reader in a region where the irradiation of the original is effectuated.
2. Description of the Related Art
An image reader, such as a copying machine or scanner, adapted to read original image data recorded on paper sheet or the like for subsequent various kinds of processing is generally constructed so that the original is irradiated with light beams emitted from a light source lamp such as fluorescent lamp. Light beams reflected on the original are guided to enter a light receiving station provided with a photoelectric converter device such as a CCD (Charge-Coupled Device). In the case of the image reader for a stationary original, for example, like an image scanner as described in Japanese Laid-Open Patent Application No. 1997-330395, the original is placed on the platen glass is irradiated with light beams emitted from said light source lamp which is moved relative to said original. Moving original image readers are also well known, for example, like the image reader disclosed in Japanese Laid-Open Patent Application No. 1996-125806 or the optical scanner disclosed in 1997-179213, in which the original in the course of being fed is irradiated with light beams emitted from a light source lamp placed at a fixed position. It is also well known that the image reader of a stationary original is incorporated with the original feeder mechanism to be used in the stationary original mode as well as in the moving original mode.
An image reader adapted to be used in the stationary original mode as well as in the moving original mode has usually been provided on the lid serving to cover the original placed on the platen glass with the original feeder mechanism. There is provided the light source lamp adapted to be moved to the position at which the original in the course of being fed can be irradiated with light beams emitted from this light source lamp. It is also well known that the one and same image reader is provided with the platen glass exclusively used to read the original in the course of being fed and the platen glass exclusively used to read the stationary original. As the platen glass exclusively used to read the original in the course of being fed, the band-shaped platen glass has usually been used since the original running on this platen glass is irradiated with light beams emitted from the light source lamp.
However, the platen glass exclusively used to read the original in the course of being fed has sometimes been damaged due to its band-like shape. Except when the stationary original is placed on the platen glass, this platen glass is covered and concealed with the lid and, for example, if the user carelessly puts his or her elbow upon the lid and a load exceeding a predetermined value is exerted upon the lid, the platen glass may be flexed and even broken. To avoid such flexion of the platen glass, the platen glass has conventionally been supported on a relatively thick retaining plate.
The moving original runs on the upper surface of the platen glass used to read the original in the course of being fed and, if the original can not smoothly run thereon, it is difficult to read the image recorded on this original at high accuracy. It is also well known to provide above the platen glass original feeding members such as rollers and guide members so that a gap may be ensured between the platen glass and these original feeding members including the guide members appropriate for smooth running of the original.
The original feeding members such as the guide members are mounted on the lid. When the image reader is used in the stationary original mode, after the original has been set on the predetermined position with the lid opened, the image reading is started with the lid closed again to eliminate any effect of ambient light. During operation of setting the original on the predetermined position, the original is sometimes slidably moved on the platen glass. In this case, the original may inconveniently enter the gap possibly defined between the platen glass and the other members such as the glass retaining member. To avoid this inconvenience, the platen glass must be in close contact with the other members such as the glass retaining member.
However, on account of recently increasing demand for improvement in performance as well as compactness of image readers, the conventional mechanism for retaining the platen glass used to read the original in the course of being fed may be accompanied with problems as will be described. To achieve the performance improvement of the image reader, the image recorded on the original must be sharply and clearly reproduced. To this end, it is required that the light source lamp has brightness as high as possible, and the light source lamp is located as closely as possible to the original. If the light source lamp can be placed close to the original, the image reader can be correspondingly thinned and the demand for compactness also can be satisfied. However, with the conventional platen glass retaining plate which is relatively thick, it is difficult or impossible to reduce the distance between the light source lamp and the original and thereby to satisfy the demand for improvement in performance as well as in compactness. Additionally, the relatively thick retaining plate makes weight-saving of the image reader difficult.
To avoid difficulties encountered when that the original might be inserted into a gap between the platen glass and the other members, such as the glass retaining member, it may be contemplated to keep the platen glass in close contact with the glass retaining member. However, a height of the lid on which the guide member is mounted necessarily increases by a dimension corresponding to the gap which should be ensured between the platen glass and the guide member, resulting in that the image reader may become bulky.
In view of the problems as have been described above, the present invention aims to miniaturize the image reader by improving the platen glass retaining plate used to read the original in the course of being fed so that this retaining plate can be formed as thin as possible. Furthermore, the present invention aims to provide the mechanism for retaining the platen glass exclusively used to read the original in the course of being fed in the image reader improved so that, with the lid opened, the platen glass comes in close contact with the glass retaining member to prevent the original from being inserted between these platen glass and glass retaining member and, with the lid closed, the platen glass is slightly moved downwardly to form an appropriate gap between the platen glass and the guide member of the original feeder and the original can be smoothly fed through this gap.
The object set forth above is achieved, according to one aspect of the present invention, by a mechanism for retaining a platen glass exclusively used to read an original in the course of being fed in an image reader adapted to irradiate said original with light beams from a light source lamp placed at a predetermined position, to pick up light beams reflected on said original and thereby to read an image formed on said original. The mechanism is characterized by said platen glass functioning to guide said original in an appropriately stretched and flattened state in the course of feeding said original retained by retaining means in operative association with a frame of the image reader. The retaining means comprises a glass supporting member having one end on which said platen glass is placed and supported and a member on which the other end of said glass supporting member is placed and supported and which is supported on said frame. Said glass supporting member is formed of a relatively thin plate material and said member to be supported on said frame is formed of a relatively thick plate material.
Even if a load tending to flex the platen glass is carelessly exerted upon the platen glass, the sufficiently thick members directly supported on the frame prevent the platen glass from being significantly flexed and damaged. Furthermore, the platen glass is placed and supported on the relatively thin glass supporting member, so the platen glass can be put close to the light source lamp and the original running on the platen glass also can be put close to the light source lamp. With such structure, it is possible to irradiate the original with light beams of high brightness and thereby to make the image adequately clear to obtain the image information of desired quality. In addition, the distance between the original and the light source lamp can be reduced and thereby the size of the image reader can be thinned.
The object set forth above is achieved, according to another aspect of the present invention, by a mechanism for retaining a platen glass exclusively used to read an original in the course of being fed in an image reader adapted to irradiate said original with light beams from a light source lamp placed at a predetermined position, to pick up light beams reflected on said original and thereby read an image formed on said original. The mechanism is characterized by said platen glass functioning to guide said original in an appropriately stretched and flattened state in the course of feeding said original retained by retaining means in operative association with a frame of the image reader. The retaining means comprises a glass supporting member having one end on which said platen glass is placed and supported and a member on which the other end of said glass supporting member is placed and supported and which is supported directly on said frame. Said glass supporting member is formed of a relatively thin plate material and said member supported directly on said frame is formed of a relatively thick plate material, and there is provided a magnet above said other end of said glass supporting member so that said glass supporting member is spaced from said member supported directly on said frame as said glass supporting member is magnetically attracted to and engaged with said magnet and said glass supporting member is released from a restrain under a magnetic force of said magnet and placed on said member supported directly on said frame as a load higher than a predetermined value is exerted upon the platen glass.
It is assumed that a load higher than a predetermined value is exerted upon the platen glass due to the weight of the lid having been closed to cover the platen glass. Thereupon, the glass supporting member is moved downwardly against the magnetic attraction by the magnets and placed and supported on the members directly supported on the frame. With the lid opened again, the glass supporting member is moved upwardly under the magnetic force of the magnets. More specifically, the platen glass is moved upwardly and brought in contact with the glass supporting member as the lid is opened, so any gap is not left between the platen glass and the glass supporting member into which the original might be inserted. With the lid closed, the platen glass is moved downwardly to define an appropriate gap between the platen glass and the guide member of the original feeder and the original can be smoothly fed through this gap.
According to one preferred embodiment of the mechanism for a platen glass exclusively used to read an original in the course of being fed in an image reader, shock absorbing means is interposed between said member supported directly on said frame and this frame. If a load is carelessly exerted upon the platen glass, the shock absorbing means can absorb such load and prevent the platen glass from being significantly flexed.
The object set forth above is achieved, according to still another aspect of the present invention, by a mechanism for retaining a plate-like member adapted to retain said plate-like member at a desired position in the absence of a load higher than a predetermined value, to move said plate-like member from said desired position to the other position in the presence of the load higher than the predetermined value and to move said plate-like member, upon removal of said load higher than the predetermined value, back to said desired position. The mechanism is characterized by said plate-like member formed of a magnetic substance, and there is provided a magnet so as to be opposed to said plate-like member, said predetermined position is defined by a state in which said plate-like member is magnetically attracted to and engaged with said magnet, and, under a load higher than the predetermined value, said plate-like member is disengaged from said magnet against its magnetic force. Upon removal of said load, said plate-like member is again magnetically engaged with said magnet.
When a load exceeding the magnetic force of the magnets is exerted upon the plate-like member, the plate-like member is moved from a predetermined position to the other position against the magnetic force of the magnets. Upon removal of the load, the plate-like member is forcibly moved back to the predetermined position under the magnetic force of the magnets. The magnitude of the load under which the plate-like member is disengaged from the magnets can be adjusted by selectively varying the area of the plate-like member over which the plate-like member is magnetically engaged with the magnets.
These and other features, objects and advantages of the present invention will become apparent upon reading the following description thereof together with reference to the accompanying drawings.